Traditionally, seals are used to prevent fluids from flowing between joints of rigid components. In particular examples, seals are used in pumps and between flanges to limit fluid flow out of containment regions. For example, seals along pump shafts may limit lubricating fluids or pressurized process fluids from escaping along an annulus defined by the shaft and a housing. Traditionally, such seals have been formed of malleable materials, such as graphite or metal strips in the case of flange seals or elastomeric materials in the case of shaft seals. However, traditional materials have proven ill suited for new applications, such as high pressure liquid chromatography systems.
High pressure liquid chromatography uses a high pressure liquid carrier medium to separate chemical species by moving the species across an adsorption medium. Different chemical components adsorb on and desorb from the adsorption medium at different rates resulting in separation of the components as the carrier medium moves through or around the adsorption medium. Accordingly, the effectiveness of a high pressure chromatography system may be adversely influenced by extraneous ions or particulate materials in the carrier medium. As such, new materials are being used in the formation of pumps and other components of high pressure liquid chromatography columns. Traditional sealing components using traditional sealing materials have been shown to damage pump components formed of the new materials compatible with liquid chromatography systems or have been shown to release undesirable ions or particulate materials into the liquid carrier medium, which reduce the effectiveness of high pressure liquid chromatography systems. In particular, traditional sealing materials may scratch pump shafts, damaging expensive pump components and shortening the lifespan of pumps. In another example, the traditional sealing material may release particulate material into the liquid carrier medium clogging the liquid chromatography column and reducing the effectiveness of the high pressure liquid chromatography system. In particular examples, the particulate material may act as an additional adsorption surface, adversely influencing the separation of chemical components.
As such, an improved seal material would be desirable. SUMMARY
In a particular embodiment, a seal is formed of a material including about 80.0% to about 95.0% by weight fluoropolymer, about 1.0% to about 10.0% by weight aromatic polymer, and graphite fiber.
In another exemplary embodiment, a pump includes a rod and a seal. The seal includes a surface in contact with the rod. The seal is formed of a material comprising about 80.0% to about 95.0% by weight fluoropolymer, about 1.0% to about 10.0% by weight aromatic polymer, and graphite fiber.
In a further exemplary embodiment, a composite material includes at least about 80.0 wt % modified polytetrafluoroethylene, not greater than about 10.0 wt % aromatic polymer, and at least about 1.0 wt % graphite fiber. The modified polytetrafluoroethylene includes perfluoropropyl vinyl ether in an amount not greater than about 5.0 wt %.